This project is concerned with behavioral analyses of information transmission within the spinal somesthetic pathways. The subjects will be monkeys, and the approach is to obtain psychophysical thresholds before and after a variety of spinal lesions have been administered. The proposal focuses on two long-term experiments: (1) assessment of tactual discrimination capacities that survive the spiral lesions, with emphasis on component spotial and temporal cues that should be important for somesthetic coding, and (2) evaluation of the spinal pathways responsible for recovery of pain reactivity after spinothalamic cardotomy. Histological controls will be an important part of these studies. The tactile discrimination studies on monkeys will be supplemented with human psychophysical investigations, using similar stimulus manipulations, in the attempt to efficiently define interesting phenomena of spatio-temporal resolution on the skin. Also, an investigation of pain modulation by prior stimulation of peripheral skin will be conducted in an effort to define the magnitude, duration, and distribution of the effect.